Dextran Precipitation Research Articles

The relationship between harvesting methods and dextran formation in sugarcane (Saccharum officinarum cv. Co 6806), and quality indices

The effects of harvesting conditions on dextran deterioration, and indices indicating dextran in the juice were aimed to be studied for the sugarcane variety Co 6806. Therefore, sugarcane was harvested manually after plantation and two ratoons, before and after burning as well as with and without stalk chopping. Dextran formation in juice was measured 1 to 5 days after harvest, and correlated with pH, viscosity, Brix, colour, polarization, apparent purity and Australian commercial cane sugar (CCS). Harvesting methods alone did not explain cane deterioration, but it may be due to a combination of adverse cultivation, maturation, harvesting, environment and weather conditions. Still, burning and chopping may increase the risk of deterioration, and the maximum time from harvest to processing should not exceed 4 days. Increasing viscosity (R = 614, p<0.001), and decreasing pH to 6.1–6.4 (R = 0.807, p<0.001) correlated with dextran up to 893 ppm in Brix, while colour and Brix (total soluble solids) did not change, indicating dextran precipitation. Polarization correlated with CCS (R = 0.968, p<0.001). Among these indices, pH and CCS calculated from polarization were the best in predicting elevated dextran concentrations.

Preparation and Characterization of a Novel Morphosis of Dextran and Its Derivatization with Polyethyleneimine.

Dextran, a variant of α-glucan with a significant proportion of α-(1,6) bonds, exhibits remarkable solubility in water. Nonetheless, the precipitation of dextran has been observed in injection vials during storage. The present study aimed to establish a technique for generating insoluble dextran and analyze its structural properties. Additionally, the potential for positively ionizing IS-dextran with polyethyleneimine was explored, with the ultimate objective of utilizing IS-dextran-PEI as a promising support for enzyme immobilization. As a result, IS-dextran was obtained by the process of slow evaporation with an average molecular weight of 6555 Da and a yield exceeding 60%. The calculated crystallinity of IS-dextran, which reaches 93.62%, is indicative of its irregular and dense structure, thereby accounting for its water insolubility. Furthermore, positive charge modification of IS-dextran, coupled with the incorporation of epichlorohydrin, resulted in all zeta potentials of IS-dextran-PEIs exceeding 30 mV, making it a promising supporting factor for enzyme immobilization.

Microfiltration-mediated extraction of dextran produced by Leuconostoc mesenteroides SF3

Recently, the production of metabolites from fermentation broths has been of great importance due to microorganisms are able to produce a wide variety of products and by-products; however, one of the challenging tasks is the extraction of such metabolites. The extraction with organic solvents is likely the most used methodology to recover the metabolites from the fermentation broths; which has been criticized according to the negative effect of using solvents on the environment. In this sense, physical separation methods, like membrane processes, have started to be involved in such recovery task. Thereby, we propose a membrane technology (i.e., microfiltration (MF)) for the separation of dextran produced by Leuconostoc mesenteroides SF3. Herein, a comparison between dextrans extracted with solvent extraction (i.e., ethanol) and integrated MF system is presented. The results revealed that the membrane process modified some of the physicochemical (e.g., hygroscopicity, solubility, water absorption capacity, and porosity) and morphological characteristics of the dextran. In addition, the MF process displayed a 33.5% dextran extraction yield with a saving of 75% in ethanol consumption for dextran precipitation.

Recalibration of blood analytes over 25 years in the atherosclerosis risk in communities study: impact of recalibration on chronic kidney disease prevalence and incidence.

Equivalence of laboratory tests over time is important for longitudinal studies. Even a small systematic difference (bias) can result in substantial misclassification. We selected 200 Atherosclerosis Risk in Communities Study participants attending all 5 study visits over 25 years. Eight analytes were remeasured in 2011-2013 from stored blood samples from multiple visits: creatinine, uric acid, glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, and high-sensitivity C-reactive protein. Original values were recalibrated to remeasured values with Deming regression. Differences >10% were considered to reflect substantial bias, and correction equations were applied to affected analytes in the total study population. We examined trends in chronic kidney disease (CKD) pre- and postrecalibration. Repeat measures were highly correlated with original values [Pearson r > 0.85 after removing outliers (median 4.5% of paired measurements)], but 2 of 8 analytes (creatinine and uric acid) had differences >10%. Original values of creatinine and uric acid were recalibrated to current values with correction equations. CKD prevalence differed substantially after recalibration of creatinine (visits 1, 2, 4, and 5 prerecalibration: 21.7%, 36.1%, 3.5%, and 29.4%, respectively; postrecalibration: 1.3%, 2.2%, 6.4%, and 29.4%). For HDL cholesterol, the current direct enzymatic method differed substantially from magnesium dextran precipitation used during visits 1-4. Analytes remeasured in samples stored for approximately 25 years were highly correlated with original values, but 2 of the 8 analytes showed substantial bias at multiple visits. Laboratory recalibration improved reproducibility of test results across visits and resulted in substantial differences in CKD prevalence. We demonstrate the importance of consistent recalibration of laboratory assays in a cohort study.

Formation of Dextran Deposits in Brazilian Sugar Cane Spirits

The formation of dextran deposits in sugared Brazilian cachaça was studied as a function of the time considering the effects of temperature, molecular weight (M(w)), visible light, pH, and the presence of Ca, Mg, Cu, and Fe ions in the concentrations at which they are usually present in this beverage. At 25 °C and pH 4.4, the experimental half-lives (t(1/2)) for precipitation are 73 and 124 days for dextrans with M(w) 5.9 × 10(6) and 2.1 × 10(6) Da, respectively. For dextrans with M(w) 5.0 × 10(5) and 4.0 × 10(4) Da, the experimental t(1/2) values are >180 days. For a dextran with M(w) 2.1 × 10(6) Da a change in pH from 4.4 to 5.5 at 25 °C resulted in a t(1/2) decrease from 124 to 25 days. At pH 4.4 the visible light and the presence of metal ions in average concentrations usually found in cachaças do not exhibit noticeable influence on the rate of dextran precipitation.

Comparative study of the efficacies of nine assay methods for the dextransucrase synthesis of dextran

A comparative study of nine assay methods for dextransucrase and related enzymes has been made. A relatively widespread method for the reaction of dextransucrase with sucrose is the measurement of the reducing value of d-fructose by alkaline 3,5-dinitrosalicylate (DNS) and thereby the amount of d-glucose incorporated into dextran. Another method is the reaction with 14C-sucrose with the addition of an aliquot to Whatman 3MM paper squares that are washed three times with methanol to remove 14C- d-fructose and unreacted 14C-sucrose, followed by counting of 14C-dextran on the paper by liquid scintillation counting (LSC). It is shown that both methods give erroneous results. The DNS reducing value method gives extremely high values due to over-oxidation of both d-fructose and dextran, and the 14C-paper square method gives significantly low values due to the removal of some of the 14C-dextran from the paper by methanol washes. In the present study, we have examined nine methods and find two that give values that are identical and are an accurate measurement of the dextransucrase reaction. They are (1) a 14C-sucrose/dextransucrase digest in which dextran is precipitated three times with three volumes of ethanol, dissolved in water, and added to paper and counted in a toluene cocktail by LSC; and (2) precipitation of dextran three times with three volumes of ethanol from a sucrose/dextransucrase digest, dried, and weighed. Four reducing value methods were examined to measure the amount of d-fructose. Three of the four (two DNS methods, one with both dextran and d-fructose and the other with only d-fructose, and the ferricyanide/arsenomolybdate method with d-fructose) gave extremely high values due to over-oxidation of d-fructose, d-glucose, leucrose, and dextran.

Preparation of self-assembled microspheres and their potential for drug delivery

Dextran solutions intended for use as plasma extenders have been observed to form insoluble precipitates. Earlier studies of precipitation have shown that in solutions of 50% and 60% w/w of dextran molecular mass 6000 g mol−1 beaded precipitates are formed over a two-week period. This study considers dextran precipitation over a wider molecular mass range and the kinetics, of formation, morphology and potential utility of these precipitates is investigated. Results show precipitation occurs over the dextran molecular mass range 6000–17,000 g mol−1, with lower molecular mass material showing more rapid precipitation. As bead formation is accompanied by an increase in turbidity, formation kinetics were quantified spectrophotometrically confirming that precipitation rates were inversely proportional to molecular mass. The utility of these precipitates for drug delivery applications was assessed using bovine serum albumin as a protein drug analogue. The results showed that the inclusion of protein did not prevent bead formation and that entrapped protein was subsequently released from dextran beads in a time dependant manner. This suggests that dextran beads of this type may find application in the drug delivery area, as they combine the advantages of mild entrapment conditions with the use of an unmodified clinically approved polymer.

Preparation of pore-filled responsive membranes using dextran precipitation

A novel method for the preparation of a composite pore-filled membrane based on self-assembled hydrogels is described. Responsive pore-filled membranes based on mixtures of dextran (molecular weight 6000) and the glucose binding lectin Concanavalin A (ConA) were prepared. The transport properties of these membranes were characterised using a twin chamber diffusion cell with Cibacron blue as a tracer solute. As the ConA molecules introduce affinity cross-links into the gel structure by binding to terminal glucose moieties on the dextran chains the mesh size increased as the physical cross-link density of the hydrogel decreased with increasing competing glucose concentration. This increased the gel-phase diffusion coefficient for the tracer with results obtained for the effect of glucose on transport rates showing a linear increase up to a concentration of 40 mM. Further increases in d-glucose concentration lead to a subsequent decrease in transport rate which is attributed to the effects of gel swelling increasing the diffusion path length. Control experiments conducted with l-glucose, which does not bind to ConA, showed no increase in transport rate confirming a specific competition effect.

Thermochemistry of dissolution and separation of polymers from solution

The thermal effects of dissolution of dextran in water and mixing of water with dimethylacetamide are measured by calorimetry and the thermal effect of precipitation of dextran at 298 K is calculated. A thermochemical method of determining the structural changes that take place during dissolution and precipitation of the polymer is proposed.

Small-Angle X-Ray Scattering Studies on Nucleation Formation of Dextran Precipitation in the Presence of Boron

In the present study, the nucleation formation process of dextran precipitation in the presence of boron was investigated by small-angle X-ray scattering (SAXS) techniques. The formation mechanism of aggregates or nuclei is very important in the initial step of crystallization. SAXS measurement is an excellent technique for observing these processes. The results of SAXS measurement suggest that boron, as a trace impurity, induces the aggregating of dextran molecules intermolecularly as a process in the nucleation formation of dextran precipitate nuclei and causes precipitation of dextran through an elongation process. These reactions occur readily at low boron concentrations. In fact, boron, which was detected at low levels in dextran solutions, was concentrated in the precipitates. Therefore, an aqueous solution of boron-free dextran should be resistant to precipitation.

Entrapment of dextran in plant cell capsules by reversible change of cell wall permeability.

Vesicular packing material (VP) made of clusters of extracted higher plant cells with the intact framework of their cell wall was used so far for permeation chromatography (vesicle chromatography). The objective of this study was to devise a method to entrap dextran in the vesicles. This can provide a means to entrap biocatalysts and secondly, to create aqueous two-phase systems with a stationary dextran phase for liquid-liquid partition chromatography. Dextran of molecular sizes above the separation limit of the plant cell wall cannot permeate into the intracellular space in aqueous medium. However, in hydrophilic organic solvent/water mixtures, dextran molecules can diffuse into the capsules. The removal of the organic solvent leaves the dextran trapped inside. There was an inverse correlation between the percentage of dextran permeating through the cell wall (Pperm) and the concentration of solvent required for dextran precipitation. The increase of permeability is therefore considered to be caused, to a great extent, by the decrease of the effective size of dextran molecules due to decreased solvation. Pperm was inversely correlated to the dielectric constants and the polarities of the solvents and, in the case of protic solvents, the hydrogen-bond acidities. No correlation was found to the hydrogen-bond basicities.

Antithrombin Milano: a new variant with monomeric and dimeric inactive antithrombin III

A qualitative defect of antithrombin III (AT III) has been demonstrated over three generations in eight members of an Italian family by the discrepancy between a normal amount of antigen and decreased antithrombin and anti-Xa activity in the presence or in the absence of heparin. By two-dimensional immunoelectrophoresis in the absence of heparin, two peaks of AT III were present in all patients' plasma. AT III was purified from normal and propositus plasma by sulfate dextran precipitation followed by heparin affinity chromatography. The elution profile of the patient's AT III was abnormal and allowed the separation of two populations of AT III, normal and abnormal. The first fraction (normal AT III) contained AT III activity, migrated as a single peak by two-dimensional immunoelectrophoresis and by sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE), demonstrated a single band with a molecular weight (mol wt) identical to that of normal AT III (60,000). Conversely, the last fraction, devoid of AT III activity, migrated as a single abnormal peak by two-dimensional immunoelectrophoresis in the absence of heparin. By SDS-PAGE, two bands were observed: one with a mol wt of 60,000 and a second one with a mol wt of 120,000. Western blots clearly demonstrated cross-reactivity of the 120,000 and 60,000 mol wt bands with monospecific antisera to human AT III. Reduction of the 120,000 mol wt band converted it to a single 60,000 mol wt band, suggesting the presence of an abnormal dimeric form of AT III. The name AT III Milano is proposed for this new variant.

Antithrombin Milano: A New Variant With Monomeric and Dimeric Inactive Antithrombin III

A qualitative defect of antithrombin III (AT III) has been demonstrated over three generations in eight members of an Italian family by the discrepancy between a normal amount of antigen and decreased antithrombin and anti-Xa activity in the presence or in the absence of heparin. By two-dimensional immunoelectrophoresis in the absence of heparin, two peaks of AT III were present in all patients' plasma. AT III was purified from normal and propositus plasma by sulfate dextran precipitation followed by heparin affinity chromatography. The elution profile of the patient's AT III was abnormal and allowed the separation of two populations of AT III, normal and abnormal. The first fraction (normal AT III) contained AT III activity, migrated as a single peak by two-dimensional immunoelectrophoresis and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), demonstrated a single band with a molecular weight (mol wt) identical to that of normal AT III (60,000). Conversely, the last fraction, devoid of AT III activity, migrated as a single abnormal peak by two-dimensional immunoelectrophoresis in the absence of heparin. By SDS-PAGE, two bands were observed: one with a mol wt of 60,000 and a second one with a mol wt of 120,000. Western blots clearly demonstrated cross-reactivity of the 120,000 and 60,000 mol wt bands with monospecific antisera to human AT III. Reduction of the 120,000 mol wt band converted it to a single 60,000 mol wt band, suggesting the presence of an abnormal dimeric form of AT III. The name AT III Milano is proposed for this new variant.

Murine typhus toxin: studies on identification of the neutralizing factor present in normal human serum.

Studies were made on the isolation and identification of the Rickettsia typhi toxin-neutralizing factor (TNF) previously demonstrated in normal human serum. By means of various methods of separating serum proteins, such as filtration on Sephadex G-200, dextran precipitation, hydroxyapatite chromatography, and ultracentrifugation, TNF was found to be closely associated with purified serum beta-lipoprotein, although no serological relationship with this protein was demonstrated. Lipase as well as trypsin digestion of purified preparations of beta-lipoprotein destroyed the TN activity. No evidence was obtained for an association of TNF with the immunoglobulins or with any serum protein other than beta-lipoprotein. Further studies revealed that (i) serum specimens with TN titers of 1:1024 and others with titers of 1:8 or less contained the same concentration of beta-lipoprotein; (ii) purified preparations of beta-lipoprotein isolated from TNF positive and negative sera, and which had the same protein concentration, differed as much as 250-fold in TN titer; and (iii) the TN activity of a serum could be removed by absorption with antiserum to beta-lipoprotein from a positive donor, but not with antiserum to beta-lipoprotein from a negative donor.

ALLERGY TO IRON-DEXTRAN

Letters and Comments1 January 1967ALLERGY TO IRON-DEXTRANOSCAR SWINEFORD JR., M.D.OSCAR SWINEFORD JR., M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-66-1-237_1 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptTo the Editor: The following comments seem appropriate to "Fatal Anaphylaxis After Intramuscular Iron-Dextran," which appeared in the ANNALS 65: 745, 1966.Kabat, Turino, Tarrow, and Maurer (1) reported that dextran was allergenic in man. Hehre and Sugg (2) showed that dextran formed specific precipitates with types II, XII, and XX antipneumococcal sera. It was shown in this laboratory (3-5) that specific type antipneumococcal rabbit serum sensitized sufficiently to mediate fatal anaphylaxis from 2.0 mg of dextran intravenously. Dextran desensitized sensitive guinea pigs against dextran but did not desensitize against the specific type II pneumococcal polysaccharide. Precipitation of dextran with...

Preparation and characterization of the isomaltodextrins

In the course of studies on the amylopectindebranching enzyme, R-enzyme (Hobson, Whelan & Peat, 1951; Peat, Whelan, Hobson & Thomas, 1954), it became necessary to prepare individual members of the series of glucose oligosaccharides containing the amylopectin-type branch linkage as the sole polymeric bond, i.e. the isomaltodextrins. The opportunity to do this was provided by the acquisition of a Leuconostoc mesenteroides dextran containing a very high proportion (96 %, determined by periodate oxidation) of oc-1:6-linkages. Acid-catalysed fragmentation of this polyglucose to an appropriate degree should provide a mixture ofsmall isomaltodextrins, capable of being fractionated by charcoal chromatography. This expectation has been realized and the individual members within the series isomaltose-isomaltohexaose have been isolated and characterized. The last three members, isomalto-tetraose, -pentaose and -hexaose, have not previously been described, except in terms of Rp value. The oligosaccharides described have been used in studies of the inhibition of precipitation of dextran by human antidextran (Kabat, 1956)..